Particle detectors include Micro-MEsh Gaseous or MicroMeGas Structures (hereinafter “Micromegas”). A Micromegas detector is a gaseous detector, that like other gaseous detectors, detects particles by amplifying charges that have been created by ionization in a gas volume. An exemplary Micromegas detector 8 is shown in FIGS. 1A and 1B, in which FIG. 1A shows a schematic view of the Micromegas detector 8, and FIG. 1B shows a perspective view of the micromesh 12 supported over readout strips 14. In the Micromegas detector 8, a gas volume 16 can be divided in two by the metallic micro-mesh 12, which can be placed a distance d2 above a readout electrode, strip, or micropattern array of conductive readout pads, e.g., between 25 micrometers (μm) and 150 μm. The micro-mesh 12 can allow both a high gain, e.g., of 104, and a fast signal, e.g., 100 ns, at a same time.
FIG. 1A, shows an ionizing particle or incident beam of particles 10. While passing through the detector 8, the particle(s) 10 will ionize gas atoms 20 by pulling up an electron 22 creating an electron 22/ion 20 pair. When no electric field is applied, the ion 20/electron 22 pair can recombine and nothing happens. However, when an electric field is present, such as in the order of 400 volts/centimeter (V/cm), the electron 22 can drift 24 toward the amplification electrode (micro-mesh 12) and the ion toward the cathode or cathode plane 26. When the electron 22 arrives close to the micro-mesh 12, the electron enters 22 an electric field (typically on the order of 4 kilovolts/cm (kV/cm) in the amplification gap d2). Accelerated by the electric field, the electron 22 reaches enough energy to produce ion/electron pairs that will also ionize the gas 16, creating pairs in what is known as the avalanche effect 28. Through the avalanche effect 28, several thousand ion/electron pairs are created from hundreds of primary charges, which originate from the interactions with the impinging particle, the primary charges being multiplied to create a significant signal. The electronic signal 30 is read at the readout electrode PCB anode plane 32 by a charge amplifier. The readout electrode 32 being conventionally segmented in strips and/or pixels 18 in order to obtain a position of the impinging particle in the detector 8. The amplitude and the shape of the signal 30, read via an electronic on the readout electrode or data acquisition electronics 34, can give information on the time and energy of the measured particle 10.
Thus, the incident beam of particles 10 ionizes gas 16 within detector chamber 8 drift volume d1 between the cathode plane 26 gas chamber volume cover with applied high-voltage bias HV1, producing primary ionization electrons 24. Free electrons 22 produced by ionizing particle beam 10, drift towards the biased (HV2<HV1) micromesh 12 that is located parallel to the micropattern array of conductive readout pads 18 on the surface of the array PCB anode plane 32. Once the drift electrons 22 reach the mesh 12, the greater potential difference between HV2 and the grounded array pads 18 accelerates them towards the readout array pads 18 through a narrow distance d2 while producing electron gas avalanches 28 with a high multiplication factor that is determined by the gap distance d2, a type of gas 16 used in the chamber 8, and the potential difference HV2 between the mesh 12 and array collector pads 18. The multiplied negative signal 30 can then being collected by the pads 18, and these amplified signals 30 can then be read out by the data acquisition electronics 34.
FIG. 1B shows a perspective view of the detector 8, which is a typical arrangement overview of the one-dimensional Micromegas array assembly, shown in FIG. 1A. FIG. 1B shows the planar PCB array board 32 with surface-routed readout strips 18 residing on thin regular pattern with pitch 6 of pillars 36 at a distance d2 under the parallel planar micromesh 12.